OF NATURAL HISTORY. 115 



< which had been d^phlogiflicated by the procefs of refplra- 

 <tIon, becomes again combined with phlogifton, in the 



< courfe of the circulation, it will gradually give out that heat 



< which it had received in the lungs, and difFufe it over the 



< whole fyftem.^*' 



The Do£lor afterwards proceeds to affign a reafon why 

 the heat of animals is always equal. < As animals/ fays he, 

 f are continually abforbing heat from the air, if there were 

 « not a quantity of heat carried off, equal to that which is 



< abforbed, there wcJuld be an accumulation of it in the ani- 



< mal body. The evaporation from the furface, and the cool- 



* ing power of the air, are the great caufes which prevent 



* this accumulation. And thefe are alternately increafed 



* and diminifhed, in fuch a manner as to produce an equal 



* effedl. When the cooling power of the air is diminifhed 



* by the fummer heats, the evaporation from the furface is 

 ^ increafed j and when, on the contrary, the coohng power 



< of the air is increafed by the winter colds, the evaporation 



* from the furface is proportionally diminiflied f .* 



This theory, though not fapported by mathematical evi- 

 dence, is not only ingenious, but feems to make a nearer ap- 

 poach to truth than any that has hitherto been invented f . 



Refpiration, belide being the probable caufe of the equable 

 continuation of heat in ani.nals, produces many other faluta- 

 ry and ufeful effefis in the oeconomy of animated bodies. 

 There is a moft intimate connediion between the a<St of ref- 

 piring and the circulation of the blood. When refpiration 

 is, for a fhort time, interrupted by the fumes of burning ful- 



• Crawford on Animal Heat, pag. 73. f Ibid. pag. 84. 



t If the reader is dcfirous of feeing fome pertinent reniarks on Do6lof 

 Crawford's Theory of Animal Heat, he may confult Dodtor Gardiner's Obfer- 

 vations on the Annual Oeconomy, and on the Caufes and Cure of Difeafes, ai> 

 ingenious and ufsful performance, lately publilhed, and which merits much mors 

 attention from Philofophers ^nd Phyf;ciani than it has bitherto received. 



